Here are a few tips to help you along:
If you are Pear Shaped -Skirts that gradually flare out in an A line from the waist to the ground will highlight your thin waist, while hiding the areas you don't want shown. Try to go for a more sturdy fabric that won't stick, such as Duchesse Satin or Taffeta. As for the top, try to go for a spaghetti-strap or a V neckline as this will work with the A line to make you look for slender.
If you are Busty - The best neckline to go for with this style is something with either a scooped neckline or a sweetheart neckline, do not go for something with a straight line, as this will make your bust look bigger than you'd like. Try to stay away from fabrics that have a sheen to it such as organza, satin, or silk. This will add more volume and draw attention to your bust.
If you are Plus - Sized - An Empire dress will work well for your figure, with the skirt beginning just below the bust and flowing into a gradual floor-length A line. Stay away from pleating on the fabric which is affiliated with maternity wear. The dress should compliment your shape and not sit too loose at that will add kilograms you don't have. Stick to fabrics like satin rather than anything too flowy.
If you have an Apple Shape - Go for a dress that cinches in all the smallest points on your waits line and flares out gradualy into an A shape. Something line lace detailing will create a nice corset like effect and will fit snugly. As far as necklines go, a deep neck line will be the most slimming, which will draw eyes to the vertical not the horizontal.
If you are Tall - Go for a simple silhouette, this will emphasize your natural shape. If you do decide to wear something like a long sleeve, it should go past your wrist, otherwise it will look as if the dress is too small for you. Try to stay away from too much ruffles or rosettes, less is more.
If your Straight Lined - A dress that will create curves in all the right places where you might not have them. You will look great in something like a ball gown that clinches in at your natural waist and descends into a full, flowing floor-length shirt. As far as necklines go, try to go for a dress that has some ruching to create volume, if you have a small bust.